The present invention relates to a scanning type image pick-up apparatus and a scanning type laser beam receive apparatus suitable for passively or actively scanning a wide view-field by a two-dimensional manner.
In general, in this kind of scanning type image pick-up apparatus, an image pick-up camera internally including an image pick-up element of a charge storing type is used to obtain a light wave. In this image pick-up camera, the image pick-up element has a view angle θ and therefore, a method of scanning a search range to take in the view image is adopted in case of searching a wide view.
In the image pick-up camera as described above, the image pick-up element is provided at a focus position of an optical system, and image data is obtained by taking in light waves of a visible region (e.g., 0.4 μm to 0.8 μm) and an infrared region (e.g., 3 μm to 12 μm) received by the optical system and performing photoelectric conversion thereon. Therefore, if an angle range equivalent to an instant view angle of one pixel of the image pick-up element is scanned in one direction at a speed faster than the speed at which the image pick-up element is exposed, a so-called image flow is caused and the view image obtained thereby becomes unclear.
Therefore, a conventional scanning type image pick-up apparatus adopts a reflection mirror step scanning method in which a reflection mirror is provided before an image pick-up camera and the reflection mirror is scanned in steps for every unit angle equivalent to a view angle in synchronism with the frame time of the image pick-up element, thereby to pick up light waves into an image pick-up element within one frame time (or exposure time) and to obtain a view image, or a camera step scanning method in which an image pick-up camera directly performs scanning in steps, thereby to pick up light waves into an image pick-up element within one frame time (or exposure time) and to obtain a view image.
However, if the scanning type image pick-up apparatus as described above is constructed so as to have a wide view range, a large reflection mirror is required from the limitations of the focal distance and the image pick-up distance, in case of the former method, and an optical system such as a converging lens must be a large size, in case of the latter method. Thus, in both cases, the apparatus has a very heavy weight. Therefore, in any of these methods, a large driving force is required for step scanning, and a time delay occurs when scanning is started, so that it is difficult to obtain stable view images.
For example, since a reflection mirror or an image pick-up camera has a large size and a heavy weight, it is very difficult to perform step scanning with a high speed of about an image pick-up element frame frequency 60 Hz and a frame cycle 16.7 ms, and therefore, a problem occurs in that a clear image is difficult to obtain. The same problem occurs in case of a scanning type laser beam receive apparatus.